The history of the universe — from the Big Bang to the end of the year — day by day

Tag Archives: Out of Africa

Only in the last half century or so, with the discovery of the Big Bang, has it been possible to do something like Logarithmic History. But human beings have been speculating for far longer than that on the origins of the universe, and we’ll have plenty of occasions here to pay tribute to earlier prescientific cosmologies. (The early chapters of the book of Genesis are probably most familiar to modern readers, but there are lots of others.)

Strikingly, it may be possible to reconstruct a very early interconnected set of myths concerning the world’s origin, which date back to long before the invention of writing (or farming, for that matter). This is the argument of Michael Witzel and some of his associates, set forth at length in Witzel’s ambitious recent book, The Origins of the World’s Mythologies. Witzel is an expert on the Vedas (Hindu sacred texts)* who has grown interested in wider comparisons. He argues that there are striking parallels in myths told in traditional societies across a wide expanse of the Earth. These parallels are not the product ancient archetypes welling out of the collective unconscious, but are survivals of a coherent narrative of the origins and destiny of the universe, the gods, and humans, which was told tens of thousands of years ago. This mythological narrative includes the following:

In the beginning: primordial waters / darkness / chaos / ‘nonbeing’

A primordial egg / giant

A primordial hill / island / floating earth

Father Sky and Mother Earth and their children, for four generations, defining Four Ages of creation

The Sky is raised up and severed from the Earth

The Sky and his daughter commit incest, and the hidden sun’s light is revealed

The current generation of gods defeat or kill their predecessors.

A dragon is slain by a culture hero

The Sun becomes the father of humans (later on, of chieftains), and establishes their rituals

The first humans, whose evil deeds lead to the origin of death and the great Flood

A generation of heroes and the bringing of fire / food / culture by a culture hero

The spread of humans / emergence of local nobility: local history begins

In the future: final destruction of humans, the world, the gods

A new heaven and a new earth / eternal bliss

Some elements of the myth seem to have an astronomical significance. The revelation of the sun seems to be especially associated with the winter solstice, and the slaying of a dragon, bringing rain, with the summer solstice. The Greek version of the Four Ages (and its Near Eastern antecedents) is clearly related to the movements of stars and planets.

Witzel labels the resulting mythic narrative “Laurasian mythology,” because its major elements are found mostly in Eurasia, the Pacific, and the New World. It contrasts with a Gondwanan mythology found Africa, New Guinea and Australia. (These two mythologies happen, by chance, to correspond roughly to the ancient supercontinents of Laurasia and Gondwana.) Laurasian and Gondwanan mythology overlap to some extent. Stories of a great Flood sent to punish unruly or sinful mankind, leaving only scattered mountaintop survivors to repopulate the world, are found in both.**

Witzel proposes that Laurasian mythology dates all the way back to an Out Of Africa expansion 40 thousand years ago. I have chosen fairly arbitrarily to introduce it instead at a later date. But it can’t date any later than the main settlement of the Americas by the ancestors of Amerindians.

* Witzel’s work on the Vedas has led to his being dogged by a lot of Hindu nationalists who are outraged that he thinks Indo-European languages came from outside India: an occupational hazard for the Indo-Europeanist scholar.

** When I did fieldwork several decades ago among the Ache Indians in Paraguay, they were curious about the way the story of Noah seemed to fit with their own flood story.

For all these extinctions, the most likely cause is some kind physical catastrophe: either drastic changes in the chemistry of oceans and atmosphere, or extraterrestrial events, like asteroid strikes or, just possibly, gamma ray bursts.

Competition with other organisms is another major cause of extinctions. Usually this is just part of a steady background level of extinction. But occasionally competition – and extinction rates – increase dramatically, as during the Great American Interchange five million years ago, when South American animals were swamped by North American invaders with the establishment of the Isthmus of Panama.

Earth now may be on the edge of another episode of mass extinction, a Sixth Extinction. (although rates of species extinction don’t match those of earlier ME’s). This time the cause is very different: a single species, Homo sapiens, is playing an overwhelming role. Although the pace of extinction has accelerated over the last few centuries, you can make a case that the sixth extinction began a long time ago, with the expansion of modern humans out of Africa. Australia in particular sees the disappearance of a unique fauna that evolved over more than a hundred millions of years of isolation. This fauna included monster wombats, giant kangaroos, huge flightless birds, and a marsupial version of a lion.

All of these – all land mammals, reptiles, and birds with mass of more than 200 pounds – seem to have gone extinct by around 45,000 years ago, after humans crossed the sea to settle the island continent. (Sea levels were lower then, and Australia was connected with New Guinea, but still isolated from mainland Asia.) This is not settled science. Some researchers think climate change was to blame. But I think the evidence in the case of this and later mass extinctions is strongly in favor of humans as the major agent of extinction. This is one more reason to treat the advent of our species as one of the major evolutionary transitions, comparable to the evolution of complex cells, or multi-cellular life.

Also, based on recent recalibrations of DNA mutation rates, it looks like the African/non-African split might have happened more like 100 thousand years ago than 50 thousand years ago. So the ancestors of non-African (or non-sub-Saharan-African) H. sapiens might have occupied a homeland somewhere north of the Sahara between 100 and 50 thousand years ago, before spreading through Eurasia. North Africa is one possibility. The Near East, maybe the Arabian peninsula, is another possibility. The (or “a”) homeland might be (gated, sorry) underwater, under the Persian Gulf (sea levels were lower then). Both possibilities have some archeological support. There might have been multiple homelands, and multiple expansions – south through Arabia and along the shores of the Indian Ocean, and north through the Levant and into Europe.

A recent (2015) redating of archeological finds suggests that the Levant-to-Europe corridor was part of the story. A modern stone tool technology, coming from Ksar Akil, just outside Beirut, Lebanon, dates to about 50,000 years ago, a little before much the same technology appears in Europe, in the form of the Upper Paleolithic.

And many other “details” remain to be resolved: What did interbreeding with non-sapiens mean for the evolution of H. sapiens? And just what advantage(s) did H. sapiens have that allowed him (us!) to replace other species? Stay tuned for more on Logarithmic History

You’ve probably run into some version of the factoid that there is more genetic variation in Sub-Saharan Africa than in all the rest of the world. This assertion has to be handled with care. It doesn’t necessarily apply to genes that have been under strong diverging selection pressures on different continents. Consider skin pigmentation: there is not more variation inside Africa than outside it in skin color, or in genes for skin color. Obviously. Likewise for hair form. But it’s true for neutral genetic variation, which is most genetic variation.

The simplest way to account for the broad Africa/non-Africa distinction would be to assume a large homogenous founder population in Africa, with a smallish number of people leaving Africa and going through a genetic bottleneck, thereby reducing their genetic variation. But recently we’ve been learning that the African situation is more complicated. Specifically, there used to be a lot of genetic differentiation between different regions within Africa. Recent population movements have smoothed out some of that variation, but recent work on ancient DNA has been bringing this more variegated past to light.

A case in point: the latest data imply that the Bushmen of Southern Africa separated from other African populations (East African, West African) around 260,000 years ago (at least), long before the major Out Of Africa venture by modern humans. What’s more, the very latest data imply that the Bushmen have received outside genetic input pretty recently, in the last 1-2 thousand years. This admixture, 9-22% of the ancestry of modern Bushmen, is absent from a 2,000 year old skeleton from Ballito Bay, South Africa.

The intruding population were probably pastoralists whose livestock, and a fraction of their genes, ultimately derived from the Near East. Another fraction of their genes originated in the Sahel or East Africa. And they probably spoke a language in the Nilo-Saharan or Afro-Asiatic family. These language families pop up as a substrate in East Africa, although largely overlain by the later expansion of Bantu speakers.

One implication: Bushman groups like the !Kung have often been presented as models for our Pleistocene hunting and gathering ancestors. Yet the most recent findings imply that there has been substantial interaction, including gene flow, between Bushmen and non-hunter-gatherers for some time.

A relevant result from twentieth century anthropology: when Nancy Howell did her classic work on the demography of the Dobe !Kung Bushmen, she found that, when you look at female reproductive histories, the Dobe !Kung look like a growing population, but when you look at male reproductive histories, they look like a shrinking population. There’s no contradiction here: the women, but not the men, in the population were sometimes having children by outsiders, neighboring pastoralists. The pastoralists in question were Bantu, having arrived in the last few centuries, but the latest genetic data imply that something similar was going long before the Bantu showed up. Since it’s not clear what effect this subaltern sexual status might have had on Bushman social organization, the social life of historic Bushmen may not be a good model for hunter-gatherer life before agriculture.

Only in the last half century or so, with the discovery of the Big Bang, has it been possible to do something like Logarithmic History. But human beings have been speculating for far longer than that on the origins of the universe, and we’ll have plenty of occasions here to pay tribute to earlier prescientific cosmologies. (The early chapters of the book of Genesis are probably most familiar to modern readers, but there are lots of others.)

Strikingly, it may be possible to reconstruct a very early interconnected set of myths concerning the world’s origin, which date back to long before the invention of writing (or farming, for that matter). This is the argument of Michael Witzel and some of his associates, set forth at length in Witzel’s ambitious recent book, The Origins of the World’s Mythologies. Witzel is an expert on the Vedas (Hindu sacred texts)* who has grown interested in wider comparisons. He argues that there are striking parallels in myths told in traditional societies across a wide expanse of the Earth. These parallels are not the product ancient archetypes welling out of the collective unconscious, but are survivals of a coherent narrative of the origins and destiny of the universe, the gods, and humans, which was told tens of thousands of years ago. This mythological narrative includes the following:

In the beginning: primordial waters / darkness / chaos / ‘nonbeing’

A primordial egg / giant

A primordial hill / island / floating earth

Father Sky and Mother Earth and their children, for four generations, defining Four Ages of creation

The Sky is raised up and severed from the Earth

The Sky and his daughter commit incest, and the hidden sun’s light is revealed

The current generation of gods defeat or kill their predecessors.

A dragon is slain by a culture hero

The Sun becomes the father of humans (later on, of chieftains), and establishes their rituals

The first humans, whose evil deeds lead to the origin of death and the great Flood

A generation of heroes and the bringing of fire / food / culture by a culture hero

The spread of humans / emergence of local nobility: local history begins

In the future: final destruction of humans, the world, the gods

A new heaven and a new earth / eternal bliss

Some elements of the myth seem to have an astronomical significance. The revelation of the sun seems to be especially associated with the winter solstice, and the slaying of a dragon, bringing rain, with the summer solstice. The Greek version of the Four Ages (and its Near Eastern antecedents) is clearly related to the movements of stars and planets.

Witzel labels the resulting mythic narrative “Laurasian mythology,” because its major elements are found mostly in Eurasia, the Pacific, and the New World. It contrasts with a Gondwanan mythology found Africa, New Guinea and Australia. (These two mythologies happen, by chance, to correspond roughly to the ancient supercontinents of Laurasia and Gondwana.) Laurasian and Gondwanan mythology overlap to some extent. Stories of a great Flood sent to punish unruly or sinful mankind, leaving only scattered mountaintop survivors to repopulate the world, are found in both.**

Witzel proposes that Laurasian mythology dates all the way back to an Out Of Africa expansion 40 thousand years ago. I have chosen fairly arbitrarily to introduce it instead at a later date. But it can’t date any later than the main settlement of the Americas by the ancestors of Amerindians.

* Witzel’s work on the Vedas has led to his being dogged by a lot of Hindu nationalists who are outraged that he thinks Indo-European languages came from outside India: an occupational hazard for the Indo-Europeanist scholar.

** When I did fieldwork several decades ago among the Ache Indians in Paraguay, they were curious about the way the story of Noah seemed to fit with their own flood story.

For all these extinctions, the most likely cause is some kind physical catastrophe: either drastic changes in the chemistry of oceans and atmosphere, or extraterrestrial events, like asteroid strikes or, just possibly, gamma ray bursts.

Competition with other organisms is another major cause of extinctions. Usually this is just part of a steady background level of extinction. But occasionally competition – and extinction rates – increase dramatically, as during the Great American Interchange five million years ago, when South American animals were swamped by North American invaders with the establishment of the Isthmus of Panama.

Earth now may be on the edge of another episode of mass extinction, a Sixth Extinction. (although rates of species extinction don’t match those of earlier ME’s). This time the cause is very different: a single species, Homo sapiens, is playing an overwhelming role. Although the pace of extinction has accelerated over the last few centuries, you can make a case that the sixth extinction began a long time ago, with the expansion of modern humans out of Africa. Australia in particular sees the disappearance of a unique fauna that evolved over more than a hundred millions of years of isolation. This fauna included monster wombats, giant kangaroos, huge flightless birds, and a marsupial version of a lion.

All of these – all land mammals, reptiles, and birds with mass of more than 200 pounds – seem to have gone extinct by around 45,000 years ago, after humans crossed the sea to settle the island continent. (Sea levels were lower then, and Australia was connected with New Guinea, but still isolated from mainland Asia.) This is not settled science. Some researchers think climate change was to blame. But I think the evidence in the case of this and later mass extinctions is strongly in favor of humans as the major agent of extinction. This is one more reason to treat the advent of our species as one of the major evolutionary transitions, comparable to the evolution of complex cells, or multi-cellular life.

Also, based on recent recalibrations of DNA mutation rates, it looks like the African/non-African split might have happened more like 100 thousand years ago than 50 thousand years ago. So the ancestors of non-African (or non-sub-Saharan-African) H. sapiens might have occupied a homeland somewhere north of the Sahara between 100 and 50 thousand years ago, before spreading through Eurasia. North Africa is one possibility. The Near East, maybe the Arabian peninsula, is another possibility. The (or “a”) homeland might be (gated, sorry) underwater, under the Persian Gulf (sea levels were lower then). Both possibilities have some archeological support. There might have been multiple homelands, and multiple expansions – south through Arabia and along the shores of the Indian Ocean, and north through the Levant and into Europe.

A recent (2015) redating of archeological finds suggests that the Levant-to-Europe corridor was part of the story. A modern stone tool technology, coming from Ksar Akil, just outside Beirut, Lebanon, dates to about 50,000 years ago, a little before much the same technology appears in Europe, in the form of the Upper Paleolithic.

And many other “details” remain to be resolved: What did interbreeding with non-sapiens mean for the evolution of H. sapiens? And just what advantage(s) did H. sapiens have that allowed him (us!) to replace other species? Stay tuned for more on Logarithmic History